One might think they'd put a grease zerk in those back wheels, opposite of the keyway.I use an air hammer and a pair of scissor jacks.
The jacks go between the wheel & side of the mower & get done up tight enough to take all the slack out of the axel so there is no load on the tranny .
Then lots of penetrant down the key slot and attack it with an air hammer
When the jacks slip down wire brush, steel wool on the axel, some more penetrant, work the wheel back & forth a bit.
Still stuck, then back to the jacks & air hammer.
Now a few tricks, replace the axel botl with a an allan headed cap screw to protect the end of the shaft.
Put as much weight on the end of the air hammer as you can. It should not be bouncing around, just clicking and vibrating your fingers.
Worst one I ever had was Rider Pro 25 years old and never had a wheel off. Took better than 2 days
When you replace the wheel put plenty of axel grease on the nicely cleaned axel fill the keyway shove the key in the fill it again and make sure you have the dust seal over the end.